Commit 2e4f9675 authored by Jeremy Hylton's avatar Jeremy Hylton

Rewrite scan for clarity. Add doc string and comment.

parent 3201a568
......@@ -84,7 +84,7 @@ except ImportError:
import getopt, ZODB.FileStorage, struct, time
from struct import unpack
from ZODB.utils import t32, p64, U64
from ZODB.utils import t32, p64, u64
from ZODB.TimeStamp import TimeStamp
from cPickle import loads
from ZODB.FileStorage import RecordIterator
......@@ -150,25 +150,37 @@ def read_transaction_header(file, pos, file_size):
return pos, result
def scan(file, pos, file_size):
seek=file.seek
read=file.read
def scan(file, pos):
"""Return a potential transaction location following pos in file.
This routine scans forward from pos looking for the last data
record in a transaction. A period '.' always occurs at the end of
a pickle, and an 8-byte transaction length follows the last
pickle. If a period is followed by a plausible 8-byte transaction
length, assume that we have found the end of a transaction.
The caller should try to verify that the returned location is
actually a transaction header.
"""
while 1:
seek(pos)
data=read(8096)
if not data: return 0
file.seek(pos)
data = file.read(8096)
if not data:
return 0
s=0
s = 0
while 1:
l=data.find('.', s)
l = data.find('.', s)
if l < 0:
pos=pos+8096
pos += len(data)
break
if l > 8080:
pos = pos + l
# If we are less than 8 bytes from the end of the
# string, we need to read more data.
if l > len(data) - 8:
pos += l
break
s=l+1
tl=U64(data[s:s+8])
s = l + 1
tl = u64(data[s:s+8])
if tl < pos:
return pos + s + 8
......@@ -234,7 +246,7 @@ def recover(inp, outp, verbose=0, partial=0, force=0, pack=0):
print "\n%s: %s\n" % sys.exc_info()[:2]
if not verbose:
progress(prog1)
pos = scan(file, pos, file_size)
pos = scan(file, pos)
continue
if transaction is None:
......@@ -298,7 +310,7 @@ def recover(inp, outp, verbose=0, partial=0, force=0, pack=0):
print "\n%s: %s\n" % sys.exc_info()[:2]
if not verbose:
progress(prog1)
pos = scan(file, pos, file_size)
pos = scan(file, pos)
else:
ofs.tpc_vote(transaction)
ofs.tpc_finish(transaction)
......
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